1. Field of the Invention
The present invention relates to a light-emitting device, and more particularly to an integrally formed multi-layer light-emitting device.
2. The Prior Arts
The light-emitting theory of LED takes advantages of the intrinsic properties of semiconductors, which is different from the theory of electric discharging, heat and light-emitting of an incandescent light tube. Because light is emitted when electric current forward flowed across the PN junction of a semiconductor, the LED is also called cold light. The LED has the features of high durability, long service life, light weight, low power consumption, and being free of toxic substances like mercury, and thereby it can be widely used in the industry of the light-emitting device, and the LEDs are often arranged in an array and often used in such as electric bulletin board or traffic sign.
Taiwanese Utility Model Patent No. M387375 disclosed a package structure of an array type multi-layer LED, which included a metal substrate, a package module, a lead frame, and a mask, wherein the metal substrate was disposed on the bottom of the package structure, and the package module was used for encapsulating and fixing the lead frame over the metal substrate. The LED dies were arranged in an array on the metal substrate. The lead frames were electrically connected with the LED dies. The mask covered the package module.
However, the conventional LED package structure includes a package module which is usually made of plastic resin. The heat-dissipation efficiency of the plastic resin is much less than that of metal. If the heat-dissipation efficiency is low, the lifetime and the light-emitting efficiency of the LED package structure will be decreased. Another problem existing in the prior art is that the metal substrate is not integrally formed with the package module, and thereby the manufacturing process is complicated. Accordingly, it is desirable to provide a light-emitting device capable of solving the problems existing in the conventional LED package structure, such as low heat-dissipation efficiency, high consumption of package material, etc.